More importantly, they'll want to go back to daily item limits.
You start off being able to use /one/ of your magic item dailies per day. Each milestone lets you use an additional item that day.
At paragon, you start off able to use two; at Epic, three.
Except you don't need to do that. Removing that limit was a good thing for making magic items useful to the party. Unfortunately, doing so without any other changes opened up possible abuses. They do a good job pointing those out specifically:
"First, would the item be overly useful if a player had easy access to multiples of it? Second, does the item provide a benefit that would be overpowering if everyone in the party had access to it?"
As long as you restrict items that fall into those categories - stuff that stockpiling in large quantities would be abuseable - you should be fine.